1. Field of the Invention
The invention relates generally to flexible, expandable, duct for use with household appliances, especially clothes dryers. The invention relates more particularly to a duct having one or more torque-relieving swivel connections having a simplified configuration to facilitate cost-effective construction and assembly.
2. Related Art
Flexible helical duct is widely used to direct the exhaust air of household appliances, such as clothes dryers. The flexible helical duct is typically made from a thin metal having a continuous helical ridge, separated by a continuous helical valley. The longitudinal expansion or contraction of the duct causes a rotation of the duct about its longitudinal axis. The rotation generates a torque that causes twisting and buckling of the duct. It is known to use a swivel connection at one or both ends of the duct to relieve the torque to reduce or eliminate the twisting and buckling of the duct. The known swivel connections employ a relatively complex rotary joint, which requires multiple manufacturing steps, thereby increasing the cost. Cost is an important consideration in the market success of flexible ducts. Because of the relatively large volumes and the fungible nature of competing products, a small cost advantage can provide a substantial competitive advantage. Therefore, there is always a strong desire and need to reduce cost.
Swivel connections are also found on non-longitudinally expanding duct, such as a plastic duct with a helical ridge. One such swivel connection comprises a collar that is threaded onto an end of the plastic duct and a sleeve mounted to the end of a different duct and which slidably receives and retains the collar. Other instances of prior teaching call for the threaded attachment of the end of the duct to the swivel connection. This requires complex manufacturing and assembly steps not needed with the present invention.
The invention relates to a swivel connection for connecting two ducts to each other, end-to-end, so that they are rotatable relative to each other. In one aspect of the invention, the swivel connection includes a pair of sleeves, one of which is slidable within the other. A first sleeve has a first end, a second end, and a flange spaced from the first end and extending outwardly from the sleeve. The second sleeve has a first end, a second end, and a shoulder spaced from the first end and extending inwardly from the sleeve. Both the flange and the shoulder extend a sufficient distance so that at least a portion of the flange and the shoulder abut each other upon slidable insertion of the first sleeve into the second sleeve. When thus inserted, the flange and the shoulder will prevent separation of the first and second sleeves from each other and an axial direction while permitting the first and second ducts to rotate relative to each other.
Preferably, the sleeves each have a circular cross section and the flange and shoulder will be annular and continuous. In one embodiment, the flange and shoulder are each located adjacent to the first end of the respective sleeve.
The flange and shoulder can each be formed of a rolled edge, a lip, or a simple protruding projection. Preferably, the sleeves are formed of thin metal, but they also can be formed of integrally molded plastic.